Vacuum - tight carbon bodies

ABSTRACT

A vacuum-tight body composed of at least two carbon members which are joined to one another with a layer of a gas-impermeable solder material selected from the group consisting of Cu, Ag, Au, and alloys thereof in direct contact with a rhenium layer on adjoining carbon surfaces. The body may form a collector which forms part of a vessel wall in a high capacity electric discharge vessel.

United States Patent Katz [451 Apr. 15, 1975 [54] VACUUM TIGHT CARBONBODIES 2,154,278 4/1939 Mouromtseff 313/355 2,599,179 6/1952 Ho kins313/355 X [75] Invenm Kat, Mumch, Germany 2,835,967 5/1958 Um blia29/4721 73 Assigneez Si Aktiengesellschaft Berlin 3,591,822 7/1971 Katz313/355 Munich, Germany Filedi g- 24, 1973 Primary ExaminerSaxfieldChatmon, Jr. [21] APPL N0; 459 Attorney, Agent, or FirmHill, Gross,Simpson, Van

Santen, Steadman, Chiara & Simpson [30] Foreign Application PriorityData Sept. 8, 1972 Germany 2244267 [57] ABSTRACT [52] US. Cl. 313/352;29/4725; 29/4727;

313/355 A vacuum-tight body composed of at least two carbon [51] Int.Cl. H01j 1/02; HOlj H14; H01] H38; members which are joined to oneanother with a layer HOlj 19/30; l-lOlj 19/06 of a gas-impermeablesolder material selected from [58] Field of Search ..29/472.7, 472.5,the group consisting of Cu, Ag, Au, and alloys thereof 220/2.1 T;313/317, 352, 354, 355 in direct contact with a rhenium layer onadjoining carbon surfaces. The body may form a collector which formspart of a vessel wallin a high capacity electric [56] References Citeddischarge vessel.

UNITED STATES PATENTS 896,429 8/1908 Becket 313/355 X 2 Claims, 1Drawing Figure VACUUM TIGHT CARBON BODIES BACKGROUND'OF THE INVENTION Acoating of a metal, particularly copper, is an extraorindarily suitablematerial for obtaining gastightness for vacuum purposes. Copper isnon-magnetic and thus does not interfere with magnetic fields, it isductile so as to easily allow adjustment of parts thereof, etc. However,copper has a relatively low melting point of 1084 C. and is undesirablyinfluenced when, for example, a highly focused electron beam impinges ona coating thereof positioned on a body of low thermal conductivity. Forexample, when a carbon body has its inner surface coated with copper andforms the inner wall ofa collector. such as in a traveling wave tube,the inner surface is very sensitive to sudden and high localized risesin temperature. If, on the other hand, the carbon body has its outersurface coated with copper, such outer surface has such a low radiationability in comparison with an uncovered carbon surface that only afraction of the total power dissipation is obtained from that otherwisepossible.

SUMMARY OF THE INVENTION The invention provides a gas-impermeable carbonbody which is characterized by a high reflection property and aninsensitivity to high localized thermal stresses.

It is a novel feature of the invention to form a gasimpermeable(vacuum-tight) body from at least two carbon members joined together bya gas-impermeable metal layer between adjacent solderable surfaces ofthe carbon members.

It is another novel feature of the invention to place a layer of rheniumon adjacent surfaces of carbon members, place a disc or the like of asolder material selected from the group consisting of Cu, Ag, Au, andtheir alloys at a selected location of such rheniumcoated adjacentsurfaces and subject the resultant structure to soldering conditions,such as in a vacuum or in a protective gas atmosphere, so that the discmelts and the solder material flows into contact with the adjacentsurfaces and forms a gas-impermeable metal layer joining the carbonmembers to one another.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is an elevatedcross-sectional view of an exemplary embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the exemplary embodiment, aprotective layer of rhenium is applied to the adjacent surfaces of thecarbon members prior to soldering such surfaces together with a metalselected from the group consisting of Cu, Ag, Au, alloys thereof andsimilar metals.

The process embodiment of the invention is advanta geously carried outin such a manner that the portions of the carbon members which form thejoining or sealing surfaces are soldered together in a vacuum orprotective gas atmosphere while having solder positioned therebetween.The process may also be carried out by combining the other portions ofan electric discharge vessel at the same time the carbon members aresealed together.

In embodiments wherein the ultimately formed gastight body is composedof several body parts, solders having the same or different meltingtemperatures may be used at the various surfaces being soldered.

In the drawing, those parts which are not essential to the understandingof the principles of the invention have either been omitted or have notbeen provided with reference numerals. As shown, a carbon cylinder 1 isprovided with a' closed end, as at base 4. The inner surface of thecylinder 1 is coated with a rhenium layer 3, as by a reducing depositionprocess which provides a solid protective layer of rhenium on the carbonsurface. A second carbon cylinder 2, likewise having a closed end as atbase 5 concentrically fits within the cylinder 1. The outer surface ofcylinder 2 is provided with a rhenium coating 3'. The cylinder 2 fitsfairly snugly within the cylinder 1 so that the adjacent surfaces of thecylinders are readily solderable. A solder supply, such as a relativelythick Cu-disc 6, is placed at a select location (such as between thebases 4 and 5) between adjacent surfaces of the cylinders. Afteralignment or adjustment of the cylinders with respect to one anotherand/or to a metal cylinder 7, which forms a part of a discharge vesselwall. the two carbon cylinders are soldered together in a vacuum or aprotective gas atmosphere by melting the solder. i.e. copper, andcausing the molten solder, as by capillary forces and/or the pressureexerted by the inner cylinder 2, to flow into contact with all adjacentsolderable surfaces between the cylinders and form a gas-impermeablemetal layer 8 joining such cylinders to one another via the rheniumlayers.

In certain embodiments, fluidized solid material may be caused to flowfrom an outside reservoir arranged at a suitable height, for example, byits own weight, into the space or separating line between the cylindersor a portion of the solder may be provided from an outside source and aportion provided between the cylinders.

The solder is preferably a pure metal selected from the group consistingof copper, silver, gold, similar metals and their alloys. When formingbodies composed of a multiple of parts, select portions of solder arepositioned at various solderable surfaces and each of the solderportions may be composed of different solder materials having differingsoldering temperatures for joining or soldering the different surfaces.The plurality of solder portions may also be composed of identicalsolder materials or of solder materials having substantially identicalsoldering temperatures. In this manner, for example, a carbon body maybe produced having a small cavity for the absorption of a beam currentwith an inner surface which can withstand a high temperature, above themelting point of the solder since a temperature gradient occursthroughout the body wall and the temperature drops below the meltingpoint of the solder, which in the case of Cu is l084 C.. before reachingthe gas-impermeable metal layer and yet the body has a high radiationability since its outer surface is uncoated carbon.

As is apparent from the foregoing specification. the present inventionis susceptible of being embodied with various alterations andmodifications which may differ particularly from those that have beendescribed in the preceding specification and description. For example.non-cylindrical carbon bodies may also be made gasor vacuum-tight inaccordance with the principles of the invention. For this reason, it isto be fully understood that all of the foregoing is intended to bemerely illustrative and is not to be construed or interpreted as beingrestrictive or otherwise limiting of the present invention. excepting asit is set forth and defined in the hereto-appendant claims.

,bon-body member by I claim as my invention:

1. A gas-impermeable member comprising a collector electrode which formsa housing wall portion in a high capacity electric discharge vessel,said member being comprised of at least two substantially permanentlyjoined body members composed of carbon and having adjacent contactingsurfaces;

:1 solid protective layer of rhenium or each of said contactingsurfaces; and

a layer of a metal solder composed of a metal selected from the groupconsisting of Cu. Ag, Au and alloys thereof on said rhenium layerswhereby a gas-impermeable seal is defined between said carbon bodymembers.

2. A gas-impermeable member as defined in claim 1 wherein said solidprotective layer of rhenium is positioned on the respective contactingsurfaces of the cara reduction deposition process.

1. A GAS-IMPERMEABLE MEMBER COMPRISING A COLLECTOR ELECTRODE WHICH FORMSA HOUSING WALL PORTION IN A HIGH CAPACITY ELECTRIC DISCHARGE VESSEL,SAID MEMBER BEING COMPRISED OF AT LEAST TWO SUBSTANTIALLY PERMANENTLYJOINED BODY MEMBERS COMPOSED OF CARBON AND HAVING ADJACENT CONTACTINGSURFACES; A SOLID PROTECTIVE LAYER OF RHENIUM OR EACH OF SAID CONTACTINGSURFACES; AND A LAYER OF A METAL SOLDER COMPOSED OF A METAL SELECTEDFROM THE GROUP CONSISTING OF CU, AG, AU AND ALLOYS THEREOF ON SAIDRHENIUM LAYERS WHEREBY A GAS-IMPERMEABLE SEAL IS DEFINED BETWEEN SAIDCARBON BODY MEMBERS.
 2. A gas-impermeable member as defined in claim 1wherein said solid protective layer of rhenium is positioned on therespective contacting surfaces of the carbon-body member by a reductiondeposition process.